We had an awkward moment on the River Yealm this week - engine stopped mid channel! We quickly dropped the hook and a quick check revealed 'no compression'..... the engine rotated freely by hand.

After being returned safely to our mooring I checked again.... this time there was what felt like normal compression and the engine started - but it was misfiring a little, accompanied by a slight rattle on the misfires, which I think sounded like pushrod rattle. Oil pressure is excellent. The rockers and valve assembly are liberally coated in oil.

I removed the rocker assembly to check for free movement, excess wear etc and it seemed OK. The pushrods seem straight too. When rotated by hand, all seemed ok with good compression. On attempting to start, compression was again lost.

Any ideas anyone? I'm hoping its not a bottom end / rings problem..... sticky or badly seated valves? I know I could be looking at a major spend here but I'd like to try to repair...... any guidance or diagnostic advice would be welcome! Is there a board-resident Volvo wizard?

I have the same engine type which has not been run for a few years. It had no compression. When I whizzed it over with a drill lots of carbon type debris came flying out the exhaust. I have removed the head to re-seat the valves but the head gasket is so expensive I am reluctant to 'try' it. If there is still no compression will I need another new head gasket or could I just try it with the head not fully tightened down? Ideas or experience on a post card please.